Secondhand Smoke Linked to Higher Odds of Developing Gestational Diabetes

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Should pregnant women be worried about secondhand smoke? Yes, said Mary R. Loeken, Ph.D., Research Investigator, Section on Islet Cell and Regenerative Biology at Joslin Diabetes Center.

“For the first time a large study identifies passive smoking as an independent risk factor for gestational diabetes, particularly in women who are already at risk for gestational diabetes because they have a high BMI (body mass index),” said Dr. Loeken, whose commentary on the study’s findings appears the June issue of the journal Diabetes Metabolism Research and Reviews.

Scientists at the Tianjin Medical University in China found that other people’s smoking significantly increases a woman’s risk for developing diabetes during pregnancy (gestational diabetes).

It’s known that passive smoking increases the risk of type 2 diabetes. But the link between secondhand smoke (called passive smoking) and gestational diabetes had not been positively identified.

“We know there are adverse effects of smoking during pregnancy independent of gestational diabetes, but gestational diabetes itself poses risks for the fetus and the mother,” Dr. Loeken explained. “Smoking can have serious health complications — including pre-term birth, low birth weight and dangerously high blood pressure. Gestational diabetes can also cause serious problems that should be avoided, including pre-term birth, low or high birth weight, stillbirth and delivery complications. In addition, women who develop gestational diabetes are at increased risk for developing type 2 diabetes at some time in their lives.”

For the study, scientists examined the association of passive smoking during pregnancy and its interaction with maternal obesity on gestational diabetes risk. The study involved 12, 786 women in China who underwent blood glucose testing at 24 to 28 weeks of gestation. Self-reported passive smoking during pregnancy was collected via questionnaire.
The analysis showed that 8,831 women were exposed to passive smoking during pregnancy and 7.8 percent of those women developed gestational diabetes, in comparison to 6.3 percent of the women who were not exposed to passive smoking.

After adjusting for multiple factors such as weight and age, the researchers found that the odds of developing diabetes during pregnancy were 1.29 times higher in the Chinese women exposed to secondhand smoke, compared to the women who lived in a smoke-free environment.

The chances of developing gestational diabetes were even greater (3.09 times higher) for women who were both obese and exposed to secondhand smoke, compared to the women who reported a healthy weight and no exposure to passive smoking. The study was published in the March issue of Diabetes Metabolism Research and Reviews.

“This study showed that passive smoking and obesity both independently increase the risk for gestational diabetes, and together synergize to make gestational disease more likely,” Dr. Loeken said. “In some cultures there may be much more acceptance of smoking in the workplace and the home, putting pregnant women at greater risk of gestational diabetes.”

Unfortunately, the effect of passive smoking on maternal health is greater than previously known. However, the risk of developing gestational diabetes can be greatly mitigated by avoiding passive smoking, the study authors conclude.

This research gives strength to existing reasons calling for a ban on cigarette smoking in public places and the workplace. The less smoke exposure pregnant women have the better. This is a message that public health officials should be aware of, and take efforts to implement smoke-free policies, Dr. Loeken said.

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